The present invention relates to a method and system for controlling vehicle speed, and more particularly, to a method and system for controlling vehicle speed wherein information about approaching road curves is detected and then the vehicle speed is regulated to a certain level for ensuring safety.
As is well known in the art, the tendency of recent design and development of the automobile or vehicle has been changed from developing an automobile that is normally passively operated by the driver to developing an automobile capable of active control with regard to road conditions in which it operates.
Typical examples of such developments are an anti-lock brake system (ABS), a traction control system (TCS) and a Cruise Control system, which initially obtain information about road conditions and then control themselves to cause the automobile equipped with these systems to be appropriately operated under the road conditions. For example, development of a system is underway in which a vehicle is equipped with a radar for measuring a distance from a vehicle running ahead thereof and whereby at least a minimum distance is maintained, which is normally referred to as an Intelligent Cruise Control System (Hereunder, referred to xe2x80x9cICC systemxe2x80x9d).
One example of maintaining at least the minimum distance in the ICC system is to set a time interval that it would take for the vehicle equipped with the ICC system to arrive at a position of a leading vehicle, in a case where the leading vehicle is suddenly stopped due to an emergency situation, e.g., a collision. By using the time interval, the vehicle can be controlled in such a way that it is not allowed to be closer to the leading vehicle at a distance smaller than a distance calculated by using the time interval and speed of the leading vehicle, even though the vehicle equipped with the ICC system is set to a cruising speed faster than that of the leading vehicle.
For example, provided that the leading vehicle runs at a speed of 100 km/h and the time interval is set to 3 seconds, even though the cruising speed of the vehicle equipped with the ICC system is set to a speed greater than 100 km/h, the latter is forced to run at a speed of 100 km/h, maintaining the distance from the leading vehicle at about 83 m as a minimum value.
The automatic maintenance of at least the minimum distance from the leading vehicle removes discomfort that the driver feels from frequent changes of the set speed of the Cruise Control System due to speed changes of the leading vehicle, while allowing the driver to have enough time to react against an emergency situation caused by the leading vehicle.
Although the prior art speed control system constructed in this manner can perform its assigned task, a need has continued to exist for an enhanced speed control system capable of ensuring a safe running state of the vehicle, even when the vehicle runs on a curved road. Although the prior art speed control system can force the vehicle equipped with the Cruise Control System to not run faster than the leading vehicle on the curved road, this does not provide full safety of the vehicle in a case that there""s no vehicle running ahead.
Further, development of an intelligent transit system has become an important project in many countries, wherein a road information provider (normally referred to as a xe2x80x9cBeaconxe2x80x9d) may be mounted on one side of the road for providing information about the road. The road information provider may provide information about the inclination of a road, the curvature of a curved section of the road and the distance between the vehicle and the road curve, as well as the road conditions.
The present invention provides a system for controlling a vehicle speed comprising: a target speed input section for an input of a determined target speed of a vehicle; a detection section for detecting a running state of the vehicle by using a plurality of sensors for detecting the running state of the vehicle; an actuator section for controlling the running state of the vehicle; a controller for controlling a speed of the vehicle by receiving information about the road from a road information provider that is mounted on either side of the road for provision of road information, in such a manner as to perform an inventive vehicle speed control method to be described herein; and a display section for displaying the information input to the controller, to a driver.
Further, the present invention provides a method for controlling a speed of a vehicle comprising: (a) receiving data about a curvature of a road curve and a distance to the road curve, and calculating an appropriate speed of the vehicle at the road curve; (b) determining whether a current speed of the vehicle is higher than the appropriate speed, and calculating an arrival time interval that it will take for the vehicle running at the current speed to arrive at the road curve if it is determined that the current speed of the vehicle is higher than the appropriate speed; (c) calculating a deceleration time interval that it will take for the current speed of the vehicle to be decelerated to the appropriate speed; and (d) determining, at the time when the arrival time interval which varies according to an advancement of the vehicle becomes equal to the deceleration time interval, whether the current speed of the vehicle is equal to or smaller than the appropriate speed, and forcibly decelerating the vehicle under predetermined deceleration to the appropriate speed if it is not.
Preferably, the inventive method further comprises calculating a warning time by adding a predetermined marginal time interval to the deceleration time interval, determining whether the arrival time interval is larger than the warning time and emitting signals suggesting deceleration of the vehicle at the time when the arrival time interval becomes equal to the warning time in a case that the arrival time interval is larger than the warning time.